Beamformer solicited sounding

ABSTRACT

Example implementations are directed to methods and systems employing a solicited sounding protocol that includes an efficient communication sequence for operating a wireless transceiver transmitting a sounding trigger to one or more beamformees via a forward channel, receiving at least one dedicated training signal from the one or more beamformees via a reverse channel in response to the sounding trigger, and for each of the received dedicated training signal. The method also includes estimating forward CSI derived based on the dedicated training signal from an associated beamformee; and where subsequent packets are precoded with precoding derived from the forward CSI for transmission to the associated beamformee via the forward channel. Example aspects including scheduling multiple dedicated training signals from one or more beamformees based on a single sounding trigger.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of prior filed ProvisionalApplication No. 62/667,405 filed at the United States Patent andTrademark Office on May 4, 2018 entitled “BEAMFORMER SOLICITEDSOUNDING.”

FIELD

Aspects of the present disclosure relate in general to sounding forwireless communications operations and specifically to systems andmethods for beamformer solicited sounding and operations thereof.

BACKGROUND

Home, outdoor, and office networks, a.k.a. wireless local area networks(WLAN) are established using a device called a Wireless Access Point(WAP). The WAP may include a router. The WAP wirelessly couples all thedevices of the home network, e.g., wireless stations such as: computers,printers, televisions, digital video (DVD) players, security cameras andsmoke detectors to one another and to the Cable or Subscriber Linethrough which Internet, video, and television is delivered to the home.Most WAPs implement the IEEE 802.11 standard which is a contention basedstandard for handling communications among multiple competing devicesfor a shared wireless communication medium on a selected one of aplurality of communication channels. The frequency range of eachcommunication channel is specified in the corresponding one of the IEEE802.11 protocols being implemented (e.g., “a”, “b”, “g”, “n”, “ac”,“ad”). Communications follow a hub and spoke model with a WAP at the huband the spokes corresponding to the wireless links to each ‘client’device.

After selection of a single communication channel for the associatedhome network, access to the shared communication channel relies on amultiple access methodology identified as Collision Sense MultipleAccess (CSMA). CSMA is a distributed random access methodology forsharing a single communication medium, by having a contendingcommunication device back off and retry access if a collision on thewireless medium is detected (e.g., if the wireless medium is in use).

Communications on the single communication medium are identified as“simplex” meaning, one communication stream from a single source node toone or more target nodes at one time, with all remaining nodes capableof “listening” to the subject transmission. Starting with the IEEE 802.1lac standard and specifically ‘Wave 2’ thereof, discrete communicationsto more than one target node at the same time may take place using whatis called Multi-User (MU) multiple-input multiple-output (MIMO)capability of the WAP. MU capabilities were added to the standard toenable the WAP to communicate with single antenna single stream ormultiple-antenna multi-stream transceivers concurrently, therebyincreasing the time available for discrete MIMO video links to wirelessHDTVs, computers tablets and other high throughput wireless devices thecommunication capabilities of which rival those of the WAP. The IEEE802.11ax standard integrates orthogonal frequency division multipleaccess (OFDMA) into the WAP or stations capabilities. OFDMA allows a WAPto communicate concurrently on a downlink with multiple stations, ondiscrete frequency ranges, identified as resource units.

The IEEE 802.11n and 802.11ac standards support increasing degrees ofcomplexity in the signal processing required of fully compliant WLANnodes including beamforming capability for focused communication of userdata. In order to characterize the multipath communication channelbetween the WAP and each station a MIMO sounding is conducted. Anexplicit sounding as specified in the IEEE 802.11n and 802.11acstandards consists of the transmission of a known sequence of packetsfrom the WAP to each associated station, then each associated stationprocesses the sequence of packets to perform measurements andcalculations to generate a detailed sounding response from the stationcharacterizing the communication channel between the WAP and itself. TheWAP traditionally uses the explicit sounding response to focus its MIMOantennas in a manner which improves either or both signal strength atthe station or downlink throughput thereto.

With the growing variety and number of stations on a wireless network,there is increasing need for improved sounding processes that canefficiently coordinate communication services to a larger number ofdevices while decreasing transmission overhead from sounding and theprocessing overhead required for sounding stations.

SUMMARY

Methods and systems employing a solicited sounding protocol thatincludes an efficient communication sequence, improves bandwidth forsounding dialog, and reduces processing required by beamformees amongother benefits. In an example, a transmitter determines a soundingcontrol scheme for one or more receivers, transmits a sounding triggerto the one or more receivers based on the sounding control scheme,receives at least one dedicated training signal from the one or morereceivers in response to the sounding trigger, and for each receiveddedicated training signal, the transmitter estimates forward channelstate information (CSI) derived based on the dedicated training signalfrom an associated receiver.

Example implementations include methods and systems for operating awireless transceiver include transmitting a sounding trigger to one ormore beamformees via a forward channel, receiving at least one dedicatedtraining signal from the one or more beamformees via a reverse channelin response to the sounding trigger, and for each of the receiveddedicated training signal. The method also includes estimating forwardCSI derived based on the dedicated training signal from an associatedbeamformee, and subsequent packets can be precoded with precodingderived from the forward CSI for transmission to the associatedbeamformee via the forward channel.

Example implementations include methods and systems with a wirelesstransceiver apparatus for a wireless local area network supportingwireless communications, and the wireless transceiver apparatusincluding a plurality of antenna. The wireless transceiver apparatusalso includes a plurality of components coupled to one another to formtransmit and receive chains; and a solicitor module circuit to transmita sounding trigger, via a forward channel, to solicit multiple dedicatedtraining signal from one or more beamformees, and the dedicated trainingsignals are to be processed for estimating a forward CSI fortransmission of subsequent packets to associated beamformee.

Example implementations include methods and systems for operating awireless transceiver including transmitting a sounding trigger to one ormore beamformees via a forward channel, receiving at least one dedicatedtraining signal with timing information from the one or more beamformeesvia a reverse channel in response to the sounding trigger, and for eachreceived dedicated training signal. The method also includes estimatinga forward channel state information derived based on the dedicatedtraining signal from an associated beamformee; and where subsequentpackets are precoded with precoding derived from the forward CSI fortransmission to the associated beamformee via the forward channel, anddetermining packet transmit and receive timestamps based on the timinginformation. Other embodiments of this aspect include correspondingcommunication protocols, networking systems, apparatus, and computerprograms recorded on one or more computer storage devices, eachconfigured to perform the actions of the methods.

The methods and systems are implemented using one or more networkingdevices and/or systems. Other features and advantages of the presentinventive concept will become more readily apparent to those of ordinaryskill in the art after reviewing the following detailed description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and operation of the example implementations will beunderstood from a review of the following detailed description and theaccompanying drawings in which like reference numerals refer to likeparts and in which:

FIGS. 1A-B illustrate prior art examples of WLAN channel sounding andbeamformed communications.

FIGS. 2A-D illustrate prior art sounding and packet diagram examples.

FIG. 3 illustrates a flow diagram of an example solicited soundingbeamformer process in accordance with an example implementation.

FIG. 4A illustrates a diagram of an example sounding solicitor system inaccordance with an example implementation.

FIG. 4B illustrates a diagram of an example sounding trigger frame inaccordance with an example implementation.

FIGS. 5A-G illustrate example sequences of solicited sounding inaccordance with various example implementations.

FIG. 6 illustrates a flow diagram of an example solicited soundingbeamformee process in accordance with an example implementation.

FIGS. 7A-B illustrate an example of solicited sounding with timingfeedback in accordance with example implementations.

FIGS. 8A-C illustrate an example of sounding solicited by anotherbeamformer in accordance with an example implementation.

FIG. 9 illustrates a diagram of an example networking device inaccordance with an example implementation.

DETAILED DESCRIPTION

The following detailed description provides further details of thefigures and example implementations of the present application.Reference numerals and descriptions of redundant elements betweenfigures are omitted for clarity. Terms used throughout the descriptionare provided as examples and are not intended to be limiting.

Traditional explicit sounding approaches start with a beamformer (e.g.,access point, transmitter, etc.) sending a pair of packets with anannouncement frame and dedicated training signal (e.g., a Null DataPacket Announcement (NDPA) followed by a null data packet (NDP)) to abeamformee (e.g., station, client, receiver, etc.) so that thebeamformee can measure the received dedicated training signal forcharacteristics of the forward communication channel (e.g., from thebeamformer to the beamformee). The beamformee then traditionallygenerates a detailed sounding feedback payload that is returned to thebeamformer. The beamformer traditionally uses the returned soundingfeedback to determine precoding that can be used for subsequenttransmissions to the beamformee. The beamformer uses the soundingfeedback to improve subsequent transmissions.

In the complex multi-path channel environment encountered by multipleinput multiple output (MIMO) transmissions the feedback of link channelmatrices consumes a considerable amount of airtime due to amount of datathat has to be transmitted to characterize the multipath channel and alow modulation and coding schema (MCS) at which the conventionaldetailed sounding feedback is transmitted consuming considerable networkresources. Thus, each explicit sounding consumes precious airtime of thenetwork.

Since explicit sounding uses sounding feedback for the forward channelto determine precoding for the forward channel, explicit sounding isgenerally more accurate than estimating the forward channel based on thereverse channel as in implicit sounding. However, explicit soundinggenerally requires additional overhead and the sounding feedbackreceived from beamformee can be rather large and thus reducesavailability of airtime for other transmissions.

Traditional implicit sounding approaches start with a beamformeeopportunistically sending packets to the beamformer so that thebeamformer can measure the received packets to determine characteristicsof the reverse channel information (e.g., from the beamformee to thebeamformer) that are then used to attempts to estimate the forwardchannel back to the beamformee. However, traditional implicit soundingfails to manage sounding among several beamformees in an efficientcoordinated framework. For example, since in traditional implicitsounding approaches the beamformee controls initiation of a soundingprocess, the beamformer is unable to update the CSI as datacommunications degrade. Further, the beamformee in implicit soundingapproaches is only interested in its own sounding process and fails toaccount for the sounding needs of other station or network resourcesover time.

With the growing variety and number of nodes on a wireless network,there is increasing need for improved sounding protocols that canefficiently coordinate communication services to a larger number ofdevices while decreasing transmission overhead from sounding and theprocessing overhead for sounding required by client nodes (e.g.,beamformees).

Aspects of example implementations described herein relate to systemsand methods for a solicited sounding framework that is initiallyinitiated by the beamformer, requires minimal processing resources bythe beamformees, and can coordinate multiple soundings sequences amongseveral beamformees. The solicited sounding framework provides improvedtransmission overhead for sounding and reduces the processing overheadfor sounding required by beamformees. In an example implementationdescribed herein, a beamformer transmits a sounding trigger to solicit adedicated training signal frame from the beamformee. A sounding triggeris a packet sent by a transmitter to at least one targeted station thatinstructs the station(s) to send one or more dedicated training signalsto the transmitter. A single sounding trigger can indicate for thestation to send a number of dedicated training signals and/or a schedulefor sending the dedicated training signals along with other configurableparameters related to the dedicated training signals or transmissionthereof. A single sounding trigger can also indicate for multiplestations to send a number of dedicated training signals.

A dedicated training signal is a packet sent by a beamformee to thebeamformer that does not require a payload. A transmitted dedicatedtraining signal can be processed to estimate channel information betweena sender and recipient. The beamformee processes sounding trigger andresponds with one or more dedicated training signals to be sent atcoordinated times based on the instructions indicated by the soundingtrigger.

The beamformer can receive multiple responses to a single soundingtrigger without additional prompting of beamformees. The soundingtrigger can include additional instructions for responding and does notrequire the beamformer to send an announcement packet with the soundingtrigger or prompting for additional dedicated training signals. Thebeamformee responds to the sounding trigger with one or more dedicatedtraining signal based on the instructions accompanying the trigger. Thededicated training signal requires substantially less overhead thantraditional sounding feedback.

Example aspect of the solicited sounding framework include an efficientsounding sequence between an access point and one or more stations byreducing the number of transmissions to initiate soundings as well asthe amount of bandwidth or airtime for determining CSI for the forwardchannel as compared to explicit sounding.

In the solicited sounding framework, the beamformee (e.g., a station,receiver, etc.) sends the dedicated training signal to a beamformer(e.g., an access point, transmitter, a transceiver station, etc.) thatcan be processed to estimate reverse channel information about thechannel in the direction of the beamformee to the beamformer. Thebeamformer measures the received dedicated training signal to determinecharacteristics of the reverse channel information (e.g., from thebeamformee to the beamformer) that are then used to attempts to estimatethe forward channel back to the beamformee.

The solicited sounding framework has improved performance and efficiencyover traditional explicit sounding and traditional implicit sounding.For example, the solicited sounding framework uses a single soundingtrigger rather than requiring the beamformer to send multiple packets(e.g., NDPA and NDP) and prompts. Further, the dedicated training signalallows the beamformee to respond with minimal processing and bandwidthrather than requiring measurement of the channel, generation of detailedsounding feedback, and transmission of a large set of detailed soundingfeedback (e.g., compressed feedback reports) that can consumesignificant processing and network resources.

Moreover, the solicited sounding framework allows the beamformer toinitiate the sounding process and coordinate several dedicated trainingsignals from multiple beamformees over a period of time rather thansending several prompts or waiting for the beamformee toopportunistically send packets. Additional aspects of the solicitedsounding framework, as discussed herein, include coordinated soundingfor several receivers with different capabilities, configurable soundingcharacteristics, integrated ranging capabilities, etc.

In an example implementation, a wireless transceiver transmits asounding trigger to one or more beamformees via a forward channel,receives at least one dedicated training signal from the one or morebeamformees via a reverse channel in response to the sounding trigger.For each of the received dedicated training signal, the transceiverestimates forward CSI derived based on the dedicated training signalfrom an associated beamformee to improve transmission of subsequentcommunications of data an associated beamformee (e.g., data packetsprecoded with precoding derived from the forward CSI for transmission tothe associated beamformee via the forward channel).

The solicited sounding framework enables improved quality of datacommunications by instructing the beamformee to send multiple dedicatedtraining signals over time without additional prompts so that thebeamformer can use the multiple dedicated training signals to re-soundthe link with updated CSI. Further, the beamformer can send updatedsounding triggers to maintain coordinated sounding sequences with theone or more beamformees to efficiently maintain communication linkswithin the network. In an example, the beamformer sends another soundingtrigger in response to detecting changes in transmission quality,network resources, or performance of one or more of the beamformees. Forexample, as data communications degrade with one or more of thebeamformees, the beamformer can send another sounding trigger to updatea sounding interval or training signal format indicated by a previoussounding trigger.

In other example implementations, the efficiencies of the solicitedsounding framework can be utilized for streamlining or supporting othernetworking applications (e.g., motion tracking, building automation,etc.) in addition to sounding. In an example, the transmission betweenthe beamformer and beamformee of the solicited sounding framework can beadapted to efficiently synchronize timing between stations, rangingfunctions, etc.

FIGS. 1A-B illustrate prior art examples of WLAN channel sounding andbeamformed communications. FIG. 1A illustrate channel soundings withintermittent sounding packages sent from the WAP identifying one or morestation nodes from which prior art sounding feedback is requested.Traditional soundings packages include multiple elements including anannouncement packet with a probe packet (e.g., an NDP sounding packet).The response to each intermittent sounding packages from the recipientstation node contains detailed information that quantify thecharacteristics of the channel between it and the station node. Thetransmitter processes this detailed information. Soundings packages,whether sent from a device with a single antenna or multiple antenna,exhibit RF signal strengths to allow the recipient device to identifythe link channel characteristics.

In FIG. 1A the WAP 102 is shown setting up communication links 120 and140 with wireless station nodes 108 and 112 respectively within location100. Each link pair exchanges capabilities, (e.g., 122A-B on link 120and capabilities exchange, 142A-B on link 140). During this exchange thenumber of antenna, the number of streams, the coding and beamformingsupport capabilities of each device are exchanged. Next an initialexplicit sounding request and response takes place, 122C-D on link 120and 142C-D on link 140. The sounding package is sent using a radiofrequency (RF) signal strength 104. Upon receipt of the soundingpackage, the recipient station(s) determine changes in amplitude andphase to the sounding transmission brought about the link channel e.g.fading, attenuation, and phase shift and passes indicia of these channelcharacteristics as detailed sounding feedback response packet(s), 122D.142D, back to the WAP where they are immediately used to set upbeamforming of subsequent data communications as shown in FIG. 1B.

The IEEE 802.11n and 802.11ac standards support increasing degrees ofcomplexity in the signal processing required of fully compliant WLANnodes including beamforming capability for focused communication of userdata. One of the many capabilities of a fully compliant WLAN node undereither of these standards is the ability to focus the signal strength ofa transmitted communication toward a receiving device. Doing so requiresmultiple antenna and means for independently controlling the phase andamplitudes of the communication signals transmitted thereon. A basebandcomponent of the WAP or station called a spatial mapper takes as inputthe independent communication streams for each antenna together with asteering matrix, a.k.a. beamforming matrix, determined during a priorsounding of the channel as shown in FIG. 1A. The steering matrixcontains complex coefficients corresponding to the discrete phase andamplitude adjustments to each antenna's communication streams whichprovide the required focused signal strength to the composite of thesignals transmitted from all antennas. The steering matrix used forsubsequent transmissions is derived from the prior sounding as shown inFIG. 1A.

In FIG. 1B the WAP is shown using the sounding feedback to set upsubsequent data communications with its link partners, e.g. stations108, 112. Based on supported capabilities of the transmitter andreceiver, the detailed sounding feedback is used to establish subsequentbeamformed data communications. Beamforming increases the receivedsignal strength and is achieved by independent changes in phase and oramplitude of the signal transmitted from each of the transmit antennaswhich collectively steer the transmit power footprint toward theintended recipient station(s), using the CSI obtained in the detailedsounding feedback response packets (See e.g., 122D, 142D of FIG. 1A).

A detailed sounding feedback response packet is typically received inresponse to each sounding package. WAP 102 is illustrated at time tousing multiple antenna to beamform 105A downlink data communicationpackets 142E on link 140 to station 112. Subsequently at time ti WAP 102is illustrated beamforming 105B downlink data communication packets 122Eon link 120 to station 112.

FIGS. 2A-D illustrate prior art examples of sounding and a packetdiagram. FIG. 2A illustrates a Prior Art sounding diagram. Wirelesscommunication protocols prescribe that packet headers include variouspreamble fields with known sequences to allow a receiving station tosynchronize reception with packet boundaries and to determine thereceived channel. A typical operation of a WAP includes transmitter andreceiver sounding sequence that starts with a pair of packets (e.g., anannouncement and an NDP) that can be sent periodically (e.g. at 100millisecond intervals) to start a sounding sequence, followed by a ShortInterframe Space (SIFS), and a sounding response. During the soundingsequence one or more downstream or upstream links are probed todetermine the channel characteristics thereof and using the CSI in thefeedback from the sounding the beamforming matrix for each link subjectto the sounding is determined. The soundings are conducted on a per linkbasis, and further may be either a downlink or an uplink sounding. Thesounding feedback is different for each link. During the contentionbased interval carrier sense multiple access (CSMA) is used as a mediumaccess control (MAC) methodology to allow any station to seize controlof the channel and send uplink user data communications thereon to thetransmitter 202.

Conventional explicit sounding protocols have the transmitter 202 sendsounding packages with announcement frames 211, null data packet (NDP)212 frames, and response frames as illustrated in 200A, 200B, and 201Cof FIGS. 2A and 2B. A traditional sounding package includes a pair ofpackets where the NDPA 211 packet precedes a NDP 212 packet andidentifies the receiving station(s) 208 which are requested to share thechannel analysis (e.g., CSI) performed by the beamformee (e.g.,receiving station 208) with the beamformer (e.g., transmitter 202).

In the pair of packets, the NDPA 211 indicates which stations are torespond to the next NDP 212 sounding frame and describes the NDP framedimensions. Following the NDPA 211, the transmitter 202 sends thesounding NDP 212 as a broadcast to be processed by the identifiedreceiving station(s) 208. In response to receiving the NDP 212broadcast, the identified beamformee performs a series of steps tomeasures the RF channel characteristics, process, and generate asteering matrix with channel measurements as parts of a detailedsounding feedback response packet 250. After the beamformee receivingstation(s) 208 completes the series of steps, the station 208 respondsto the NDPA 211 and NDP 212 with a detailed sounding feedback responsepacket 250.

FIG. 2B is a Prior Art sounding diagrams 200B and 201B of explicitsounding for sequential soundings and data communication. An explicitsounding of the link channels between the transmitter 202 and station208 and the transmitter 202 and station 209 are shown in 200B and 201B.The sounding sequence includes the transmitter 202 sending the pair ofsounding packets, NDPA 211 and NDP 212, and in response the targetedstation 208 (after significant processing 260) sends back a compresseddetailed sounding feedback response packet 250A. The transmitter thenmust send a report poll packet 213 at time to prompt the next station209 from which detailed sounding feedback generation is requested.

A header of the NDP packet 212 contains a ubiquitous preamble field thatis used for channel estimation, which in the case of the IEEE 802.11acstandard is identified as a VHT-LTF field of FIG. 2C. The VHT-LTF field(e.g., a channel estimation or sounding field), contains a long trainingsequence used for MIMO channel estimation by the receiver station 208.Each recipient station 207, 208, 209 is then required to determine thecorresponding beamsteering matrix required to adjust the phase andamplitude for subsequent MIMO transmissions by the transmitter 202 so asto update the received signal strength at the receiving station.

Each beamformee station 207, 208, 209, is required to performsignificant processing of the NDP 260 to determine the detailed soundingfeedback based on matrices by performing a singular value decomposition(SVD) on the H matrix for each sub-channel or tone that requiresconsiderable processing resources (e.g., power, time, processor cycles,memory, etc.) to complete. The Signal-to-Noise Ratio (SNR) matrix isderived by scaling the SVD's sigma L matrix. Then each station waits forthe transmitter to send another packet (e.g., a report poll 213) toprompt a response, and only then does the beamformee station send asingle detailed sounding feedback in response to each report poll 213.That is, a first target station 208 only responds with a detailedbeamforming feedback packet 250B containing CSI (e.g., a payload) whenprompted. If the receiving station is IEEE 802.11n compliant thedetailed feedback is in the form of the link channel matrix H. If thereceiving station is IEEE 802.11ac compliant, the detailed feedback isin the form of the actual unitary beamsteering matrix V and the per tonediagonal matrix SNR. Any remaining stations targeted by the initialsounding, respond with the beamsteering matrix for their own link whenasked to do so by the report poll 213. The next station 209 thenresponds with compressed detailed sounding feedback response packet251B. Following the sounding, communications resume and downlinkcommunication of user data is sent on the link(s) that have beensounded. Since each station 207, 208, 209 sends detailed soundingfeedback reactively to each transmitter request, considerable bandwidthis consumed to maintain a large number of stations with frequentsounding sequences.

In response to each additional sounding packets 211 and 212, abeamformee 209 can send additional detailed beamforming feedback packets251B, 252B, etc. In some approaches, the beamformee 209 can sendadditional detailed beamforming feedback packets 251B, 252B, in responseto each prompt (e.g., report poll 213).

The user data packet(s) 266 (e.g., media access control (MAC) ServiceData Unit (MSDU) or Protocol Data Unit (MPDU)) are sent using precodingbased on an associated beamforming matrix. Transmitter 202 resumessending user data packets 266 on the link(s) that have been sounded. Thetime and overhead required to send the detailed sounding feedbackresponse packets 250A and 251B consumes substantial processing andtransmission resources.

FIG. 2C a Prior Art packet diagram of a transmitter packet with apreamble field that is used for channel estimation. FIG. 2C includes apacket 240 and the corresponding symbol interval (SI) required totransmit each field. The header includes a legacy portion containing theL-STF, L-LTF and L-SIG fields and a very high throughput portioncontaining the VHT-SIGA, VHT-STF, VHT-LTF and VHT-SIGB fields. Thepayload portion contains no user data. The legacy (L), long (LTF) andshort (STF) training and signal (SIG) fields are compatible withstations supporting only the IEEE 802.11n or earlier standards. Theremaining signal and training fields are intended for very highthroughput (e.g., IEEE 802.11ac compliant devices). The VHT-SIGA fieldcontains information on the MCS and number of streams of the sounding.The VHT-STF field is used for automatic gain control (AGC). The VHT-LTFfield (e.g., the channel estimation), includes a long training sequenceused for MIMO channel estimation by the receiver.

FIG. 2D is a diagram of sounding channels between an access point astransmitter 202 and one or more stations 208, 209. The access point andstations can be a transceiver including both a transmitter and areceiver that are combined and share common circuitry or a singlehousing. The access point and stations can also be atransmitter-receiver with separate circuitry between transmit andreceive functions. A beamformer generally includes multiple antennas fora transmitter and a receiver while a beamformee may function with asingle antenna or multiple antennas.

In an example where the access point transmitter 202 is the beamformersounding beamformee station 209, the sounding channel can be describedhaving both a forward channel 220 from the beamformer access point 202to the beamformee station 209 and a reverse channel 221 from thebeamformee station 209 to the beamformer access point 202. As shown inFIGS. 2A and 2B the beamformer access point 202 traditionally sends thepair of sounding packets with the NDPA announcement 211 and NDP sounding212 via the forward channel 220 that is received by the beamformeestation 209. The beamformee station 209 traditionally after processingthe pair of sounding packets and then sends the detailed soundingfeedback 250A, 250B, or 251B via the reverse channel 221.

Multiple stations 208, 209 can also sound each other for example as in amesh network. In an example where the station 208 is the beamformersounding beamformee station 209, the sounding channel can be describedhaving both a forward channel 230 from the beamformer station 208 to thebeamformee station 209 and a reverse channel 231 from the beamformeestation 209 to the beamformer station 208. Thus, the beamformer station208 sends the pair of sounding packets with the NDPA announcement 211and NDP sounding 212 via the forward channel 230 that is received by thebeamformee station 209. The beamformee station 209 traditionally, afterprocessing the pair of sounding packets, then sends the detailedsounding feedback via the reverse channel 231.

Traditional explicit sounding requires the beamformer to send multiplepackets to the beamformee, that then the beamformee must process eachthe multiple packets to generate detailed sounding feedback that arethen returned when prompted. The multiple packets consume airtime of theforward channel 220 preventing the transmitter from using thosecommunication resources for delivering actual user data to otherstations. The detailed sounding feedback consumes significant processingcycles (e.g., 260), power of the beamformee, and bandwidth of thereverse channel 231. Regular sounding sequences with a beamformeestations that has limited resources can diminish the utility andusefulness of such station. Further, for networks with numerousstations, sounding with multiple packets and detailed sounding feedbackwastes bandwidth and distracts the access point from effectivelycoordinating services for the growing demand of stations. Moreover,additional detailed sounding feedback packets are sent in response toreceiving additional prompts from the beamformer.

FIG. 3 illustrates a flow diagram of an example solicited soundingbeamformer process in accordance with an example implementation. Thesolicited sounding framework allows a beamformer to initiate thesolicited sounding process in a coordinated scheme for severalbeamformee stations with different capabilities and configurablesounding characteristics. The solicited sounding framework furthercoordinates the beamformee stations to automatically update thebeamformer with information to accurately precode user data withoutrequiring the beamformer to send repeated requests or prompts for theupdates.

The beamformer process can start at step 310 to determine soundingcontrols for one or more beamformee(s). In an example implementation,sounding controls can include sounding schedule instructions, trainingoptions, and station information as discussed in reference to FIGS. 4-8.Since the solicited sounding framework is initially initiated by thebeamformer, it can coordinate multiple soundings sequences among severalbeamformees and reduces the processing overhead for sounding required bybeamformees. The solicited sounding framework provides improvedtransmission overhead for sounding and requires minimal processingresources by the beamformees.

The sounding schedule and the training options can be based oncommunication parameters, for example, a beamformee's capabilities(e.g., beamforming, MIMO, etc.), traffic type (e.g., web browsing, videostreaming, video conferencing, etc.), or positioning parameters (e.g.,movement, dwell time, etc.). In an example implementation, the soundingschedule enables the beamformer to instruct the beamformee to sendmultiple dedicated training signals at scheduled sounding intervals in acoordinate manner and avoids sending multiple sounding trigger requests.The beamformee receives the sounding trigger with sounding instructionsand provides an initial dedicated training signal response that does notrequire a payload or significant processing by the beamformee. Thebeamformee can store the instructions and execute the schedule toprovide additional dedicated training signals without needing to receiveadditional sounding triggers or prompts. For example, the beamformer candetermine sounding controls to include a sounding schedule with a shorttime interval for a receiver that previously received video conferencingtraffic data.

At 320, the beamformer process transmits a sounding trigger to one ormore beamformees based on the sounding controls. For example, the singlesounding trigger can be a null data packet polling frame that is notpreceded by an announcement frame. Unlike traditional explicit soundingtechniques, solicited sounding enables the beamformer to triggerrepeated information based on a single sounding trigger rather than aNDPA and NDP.

At 330, the beamformer process receives at least one dedicated trainingsignal from the one or more beamformees in response to the soundingtrigger. In solicited sounding the beamformee does not measure channelinformation from the received sounding trigger. The one or morededicated training signals sent by the beamformee are triggered by thesounding trigger, but dedicated training signal does not requiremeasurements associated with the transmission of the sounding trigger.For example, the dedicated training signal can be a null data packetwithout a payload of sounding data.

At 340, for each received dedicated training signal, the beamformerprocess performs steps 350 and 360 to estimate a forward channel stateinformation. At step 350, the beamformer process calculates a CSI for areverse channel by measuring the received dedicated training signal. At360, the beamformer process derives a CSI for the forward channel, fromthe CSI of the reverse channel in view of characterization of front endparameters of the transmitter. In an example implementation, thebeamformer process can use the estimated forward CSI at 370 to transmitsubsequent packets using precoded packets with precoding derived fromthe estimated CSI. The beamformer process repeats, at least steps 350and 360 for each receive dedicated training signal. Accordingly, thesolicited sounding framework requires less beamformee processing andless bandwidth than traditional sounding approaches.

FIG. 4A illustrates a diagram of an example sounding solicitor system inaccordance with an example implementation. The solicitor system 410includes a trigger generator 415, a scheduler 420, a training optionsmodule 430, and a beamformee manager 440 for transmitting a soundingtrigger to one or more beamformee. In an example implementation, thetrigger generator 415 can create a sounding trigger that includessounding controls such as sounding schedule instructions, trainingoptions, and station information for the one or more receivers. Forexample, training options for the beamformee to format the dedicatedtraining signal can include repeated symbols, partial bandwidth, anumber of bits, etc.

The trigger generator 415 uses the beamformee manager 440 to determinestation information for a sounding trigger including a list of receiversto respond to the sounding trigger. The beamformee manager 440 candetermine characteristics of stations that are to receive a soundingtrigger from the transmitter. In some examples, the stations may beassociated with the transmitter such that a successful handshake orauthentication process has been attempted or successfully completed. Thebeamformee manager 440 can also deduce characteristics or assignidentifiers to stations unassociated or authenticated with thetransmitter. In some implementations, the beamformee manager 440 uses adata store 402 or a profiler module 470 to track or predictcharacteristics of stations. For example, the beamformee manager 440 candetermine a station identifier (ID), capabilities of a station, astation type, a traffic/service type, location information, a predicteddwell time, etc. Further, the beamformee manager 440 can use capturedMAC address information to determine or assign an identifier to astation. Using the beamformee manager 440, trigger generator 415 caninclude instructions in the sounding trigger that are targeted fordifferent receivers.

In an example implementation, the trigger generator 415 can includedifferent scheduling instructions in the sounding trigger that aretargeted for different receivers. The beamformee manager 440 performsfunctions for coordinating and updating operations of the other modulesof the solicitor system 410. For example, the beamformee manager 440works with the scheduler 420 to generate a list of one or more receiversassociated with a sounding trigger.

The scheduler 420 can generate scheduling instructions for individualtargeted receivers or groups of receivers to provide dedicated trainingsignals in a coordinated matter. For example, the scheduler 420 cangenerate scheduling instructions for different receivers to respondsimultaneously in response a sounding trigger at different spatialstreams. The solicitor system 410 can create various schedulingconfigurations as further discussed in reference to FIG. 5 herein.

In an example implementation, the trigger generator 415 can includescheduling instructions in the sounding trigger for groups of receiversand/or allow receivers in a group to determine a coordinated responsetime or interval. The beamformee manager 440 can identify groups ofreceivers and the scheduler 420 generates sounding instructions for thegroup in accordance with the beamformer process discussed in referenceto FIGS. 3-5 herein.

In an example implementation, the trigger generator 415 can includetraining options in the sounding trigger for formatting the dedicatedtraining signal by the one or more receivers. The beamformee manager 440can operate with the training options module 430 to generateinstructions for different receivers to respond to a sounding triggerwith a dedicated training signal in a specific format or communicationmeans (e.g., repeated symbol, spatial stream, partial bandwidth, anumber of bits, etc.). The training options module 430 can alsoconfigure a set of training options in the sounding trigger based oncharacteristics of the transmitter, observed network behaviors orperformance, environmental factors, feedback quality, etc.

The trigger generator 415 generates a sounding trigger for one or morereceivers to solicit dedicated training signals with minimal overhead.In response to a single sounding trigger, the solicitor system 410 canreceive multiple dedicated training signals from a single receiverand/or multiple different receivers.

The solicitor system 410 includes a front end controller 445, adedicated training signals tracker module 450, a reverse channel CSImodule 455, a calibration module 460, and a precoder 465 to processreceived dedicated training signals.

The front end controller 445 and the dedicated training signals trackermodule 450 can operate with the beamformee manager 440 for handlingmultiple dedicated training signals received simultaneously. Forexample, the front end controller 445 can receive multiple dedicatedtraining signals simultaneously at different spatial streams, thededicated training signals tracker module 450 can queue the receiveddedicated training signals and associate them with a station profile orstation information based on information from the beamformee manager440.

The dedicated training signals tracker module 450 processes the receiveddedicated training signals with to measure channel information from eachdedicated training signal, and the reverse channel CSI module 455calculate CSI of the reverse channel from the measured dedicatedtraining signal information. The calibration module 460 derives forwardCSI for the forward channel from the reverse channel CSI utilizing thecharacteristics of the transmitter from the front end controller 445.Characteristics of the transmitter from the front end controller 445 canbe based on specific hardware or software configurations of thetransmitter such as manufacturing process variances, design parameters,transmit times or delays in RF hardware and band to antenna, delaydifference between multiple chains of transmission, etc. The precoder465 then uses precoding derived from the forward CSI for subsequenttransmissions to the associated receiver via a forward channel.

Example implementations of the solicitor system 410 can also include aprofiler 470, a mapper 475, and a timer module 480. The profiler 470 cantrack traffic with each station to generate historical information forpredicting optimal configurations for sounding triggers. For example,based on a station's historical usage schedule or movement, the profiler470 can indicate to the scheduler 420 an optimal time interval forscheduling repeated dedicated training signals in response to a singlesounding trigger.

The mapper 475 can optimize sounding communications with stations ofdifferent capabilities. For example, the mapper 475 can coordinate withthe front end controller 445 to receive dedicated training signals frommulti-user MIMO (MU-MIMO) capable receivers, beamforming receivers, etc.The timer 480 support ranging operations with minimal overhead byleveraging the solicited sounding trigger and dedicated training signalresponses. For example, the timer 480 can be used with training optionsmodule 430 to solicit a timestamp feedback with the dedicated trainingsignal from a receiver to perform ranging operations to avoid or reduceadditional triggers or request by the transmitter.

FIG. 4B illustrates a diagram of an example sounding trigger frame inaccordance with an example implementation. The example sounding trigger411 includes an initiator 416 that is a preamble to indicate for thereceiver to respond with a dedicated training signal. The soundingtrigger 411 is an individual frame that is transmitted and includes atleast the preamble initiator 416 without any announcement packet. Thatis, the sounding trigger 411 is not part of a pair of packets orpreceded by an announcement packet (e.g., a NDPA packet).

The sounding trigger 411 can include schedule information 421 created byscheduler 420 that, for example, allow for repeated responses to asingle sounding trigger 411. Types of schedule information 421 caninclude a time interval 421A, a sounding position 421B, a packet length421C, a terminator 421D, etc.

The time interval 421A of the schedule 421 indicates how often thebeamformee is to send dedicated training signals after receiving asingle sounding trigger 411. The solicitor system 410 can configure atime interval 421A to be static or dynamic based on time periods,network conditions, etc. for different beamformees receiving the singlesounding trigger 411. For example, a static time interval 421A of theschedule 421 can instruct the beamformee to repeat sending dedicatedtraining signals consistently according to a time frame (e.g., every 100microseconds). A dynamic time interval 421A of the schedule 421 caninstruct the beamformee to repeat sending dedicated training signals inbursts within a time frame or intermittently according to a timingfactor, a condition, particular channel activity, etc.

The sounding position 421B can be used to indicate when the beamformeeis to send a dedicated training signal according to a relative positionor defined position. The sounding position 421B for the beamformee tosend a dedicated training signal can be relative (e.g., an order, alocation, a rank, a group, a time slot, etc.) to one or more otherbeamformees responding to the sounding trigger 411. For example, thesounding trigger 411 can be sent to a list of beamformees and thesounding position 421B indicates a sequence for each of the beamformeesin the list to transmit a dedicated training signal. The beamformees canrepeat sending dedicated training signals by restarting the sequencewithout receiving another sounding trigger 411. In another example, thesounding position 421B indicates coordinated time positions (e.g., basedon a time scale, a reference time, etc.) for each of the beamformees torepeat sending dedicated training signals in groups or at differenttimes without receiving another sounding trigger 411.

In some implementations, the sounding position 421B indicates forbeamformee to repeat sending dedicated training signals by listening toa channel in view of the packet length 421C of the sounding trigger 411.For example, the beamformee can monitor the channel for a preamble fromanother beamformee or count the number transmissions heard from otherbeamformees, determine a preceding beamformee based on the soundingposition 421B, and calculate a time to transmit after the precedingbeamformee in view of the packet length 421C.

The schedule 421 can include a terminator 421D to indicate or signal forone or more of the beamformees to stop or suspend sending additionaldedicated training signals. In some implementations, the terminator 421Dis sent with a first sounding trigger 411 to indicate when one or moreof the beamformees are to stop or suspend sending dedicated trainingsignals. For example, the terminator 421D can indicate a number ofdedicated training signals to send without receiving another soundingtrigger. The terminator 421D can also indicate to suspend sendingdedicated training signals after a period of time or condition (e.g., aschedule expiration). Other implementations can include a secondsounding trigger 411 with the terminator 421D that signals to stop orsuspend sending dedicated training signals. The sounding trigger 411 caninclude a terminator 421D for each targeted beamformee, a subgroup oftargeted beamformees, or all responding beamformees. In another example,the sounding trigger 411 can include training options 431 configured bytraining options module 430 to, for example, instruct receivers how toformat or customize the dedicated training signal. Types of trainingoptions 431 can include precision parameters 431A, format 431B, a timingoption 431C, spatial stream 431D, etc.

For example, precision parameters 431A can indicate how often to repeatsymbols in the VHT-LTF for the purposes of averaging at the receiver. Inan example, a timing option 431C can indicate a measured time of arrivalof an incoming packet and measured time of departure of an outgoingpacket. Training options 431 can include spatial stream 431Dconfigurations for use with MU-MIMO capable receivers. Other examplestraining options 431 can include configurable format 431B elements asunderstood in the art.

The sounding trigger 411 can also include station information 441coordinated by the beamformee manager 440 to enable, for example,multiple receivers to respond to a single sounding trigger 411. Types ofstation information 441 can include a station list 441A, a stationidentifier 441B, a MAC address 441C, a station capability 441D, etc.

Example implementations of solicited sounding as described herein canuse the sounding trigger 411 containing the initiator 416 andadditionally including none, some, or all of the schedule information421, training options 431, and/or station information 441 discussedherein.

FIGS. 5A-5G illustrate example sequences of solicited sounding inaccordance with various example implementations. FIG. 5A illustrates anexample sequences 500A and 501A of solicited sounding for a targetedstation 508A. The solicited sounding process may be initiated by anaccess point 502A to sound a channel for communicating with a station508A. In the example implementation illustrate in 500A and 501A of FIG.5A, the access point 502A initiates the solicited sounding by sending anNDP Poll 510A as a sounding trigger that identifies the access point502A and the target recipient station(s) 508A.

In response receiving the NDP Poll 510A, the station 508A sends an NDP550A to the access point 502A. The NDP 550A is sent within a firstinterval (e.g., a Short Interframe Space (SIFS) or fraction of a SIFS)of the NDP Poll 510A. The access point 502A reserves the channel duringa predetermined response period for receiving the dedicated trainingsignal. This NDP 550A response packet is an example dedicated trainingsignal with no user data that can be processed to estimate reversechannel information in the reverse direction from the station 508A tothe access point 502A. The access point 502A uses the reverse channelinformation derived based on the NDP 550A to estimate the forward CSI todetermine the corresponding link matrix(s) used to adjust the forwardchannel precoding for subsequent MIMO transmissions (e.g., user data566A) by the access point 502A to the target station 508A.

FIG. 5B illustrates an example sequences 500B, 501B and 503B ofsolicited sounding burst in accordance with various exampleimplementations. In an example implementation, a solicited sounding caninclude separate sounding triggers NDP Poll 510B to solicit one or morededicated training signals (e.g., NDP 550B, 551B, 552B) from a singlestation 508B as illustrated in sequences 500B and 501B of FIG. 5B. Thebeamformer can send additional NDP Poll 511B to update (e.g., add,change, modify, cancel, etc.) instructions for single station 508Bindicated by the previous NDP Poll 510B.

The solicited sounding framework enables improved quality of datacommunications by instructing the beamformee to send multiple dedicatedtraining signals over time without additional prompts so that thebeamformer can use the multiple dedicated training signals to re-soundthe link with updated CSI. Further, the beamformer can send anothersounding trigger to maintain coordinated sounding sequences with the oneor more beamformees to efficiently maintain communication links withinthe network. For example, the beamformer can send another soundingtrigger to account for changes in transmission quality, networkresources, performance of one or more of the beamformees. In an example,as data communications degrade the beamformer can send another soundingtrigger to update a sounding interval or training signal formatindicated by a previous sounding trigger.

In another example implementation, a solicited sounding burst caninclude separate sounding triggers NDP Poll 510B and 511B to solicit oneor more dedicated training signals (e.g., NDP 550B, 551B, 552B) fromdifferent stations 508B, 509B as illustrated in sequences 500B and 503Bof FIG. 5B. The sounding triggers NDP Poll 510B and 511B can be sent toone or more stations 508B, 509B in accordance with various exampleimplementations. That is, NDP Poll 510B can be directed to a firststation 508B and NDP Poll 511B can be directed to a second station 509B.In another example, NDP Poll 510B and NDP Poll 511B can be directed toboth the first station 508B and the second station 509B. Further, NDPPoll 510B can be directed to a first station 508B and NDP Poll 511B canbe directed to both the first station 508B and the second station 509B.Alternatively, NDP Poll 510B can be directed to both the first station508B and the second station 509B and NDP Poll 511B can be sent to updatesounding instructions for one of the stations (e.g., the first station508B).

The solicited sounding process is initiated by the access point 502A tosound multiple different stations 508B, 509B with multiple soundingtriggers NDP Poll 510B and 511B. In the example implementationillustrate by FIG. 5B, the access point 502B initiates the solicitedsounding by sending a first NDP Poll 510B to a first station 508B andreceives a first NDP 550B within a first interval for sounding of thefirst NDP Poll 510B. After receiving the first dedicated training signalfrom the first station 508B, the access point 502B can initiate anothersolicited sounding by sending a second NDP Poll 511B and receives asecond NDP 551B from a second station 509B.

The first NDP Poll 510B and/or the second NDP Poll 511B can include aschedule for the respective station 508B and/or station 509B to sendadditional NDPs 552B responses without receiving additional NDP Polls.The access point 502B uses each received NDP 550B, NDP 551B, and NDP552B to estimate forward CSI derived based on each NDP for sounding theassociated station 508B or 509B. In another example implementationillustrate by FIG. 5B, a first NDP Poll 510B can be used to solicit oneor more dedicated training signals from a targeted station 508B as anNDP 550B response. Based on the received NDP 550B, the access point 502Bderives the forward CSI for the forward channel from the reverse channelCSI in view of characteristics of a radio frequency front end of thetransmitter and subsequent packets are precoded with precoding derivedfrom the forward CSI for transmission.

The NDP Poll 510B can include instructions for the targeted station 508Bto send additional NDPs without an additional NDP Poll. The access point502B can also send another NDP Poll 511B to the target station 508B tochange (e.g., modify, replace, cancel, etc.) instructions indicated by aprevious sounding trigger (e.g., first NDP Poll 510B). The second NDPPoll 511B can be can be used to update a parameter for soliciting one ormore dedicated training signals indicated by a pervious NDP Poll 510Bsent to one or more recipients.

FIG. 5C illustrates an example sequence of solicited sounding for aseries of dedicated training signal responses. In an exampleimplementation, an NDP Poll 510C can include instructions for a targetedstation 508C to send a series of NDPs 550C, 551C, 552C, without sendingan additional NDP Poll.

In an example implementation illustrate by FIG. 5C, a first NDP 550C canbe sent by the station 508C to the access point 502C as an initialresponse to the NDP Poll 510C from the access point 502C. The targetedstation 508C can send additional dedicated training signals NDP 551C andNDP 552C based on instructions included in NDP Poll 510C. To receive theadditional NDP 551C and NDP 552C, the access point 502C can maintain atimer to anticipate when to expect the additional dedicated trainingsignals and reserve a channel.

For example, the NDP Poll 510C can include instructions that coordinatewith the targeted station 508C when to expect a series of NDPs 550C,551C, 552C at fixed or variable intervals, time window, based onsatisfying a threshold condition, an external measuring resource,prediction, etc. Thus the access point 502C can receive the series ofNDPs 550C, 551C, 552C based on a single NDP Poll 510C.

FIG. 5D illustrates an example sequences of solicited sounding for aseries of dedicated training signal responses from one or more stations550D, 551D, 552D. In an example implementation, an NDP Poll 510D caninclude instructions indicating a schedule for multiple differentstations 507D, 508D, 509D to send multiple NDPs 550D, 551D, 552D withoutan additional NDP Poll. In the example implementation illustrate by FIG.5D, the NDP Poll 510D can include a schedule to indicate a responseinterval, sounding position, etc. for each when of the stations 507D,508D, 509D are to send NDPs 550D, 551D, 552D.

The NDP Poll 510D is a sounding trigger that identifies the access point502 and the target recipient station(s) 508 for the solicited sounding.Where an NDP Poll 510D is sent to more than one station, the stations507D, 508D, 509D can use the order in which the recipient stations arelisted in the instructions from the sounding trigger 510D to control anorder or position for sending NDPs 550D, 551D, 552D. For example, theNDP Poll 510D can include a list with the order or sounding position ofeach of the stations 507D, 508D, 509D. The stations 507D, 508D, 509D canrepeat sending NDPs 550D, 551D, 552D to the access point 502D accordingto the order or schedule until the schedule expires, a terminationcommand is sent, a new NDP Poll is received, or the station 507D goesoffline.

For example, scheduling instructions indicated by the NDP Poll 510D canassign stations 507D to send a first NDP 550D within a SIFS relative tothe NDP Poll 510D, stations 508D to send another NDP 551D within a SIFSrelative to the first NDP 550D, and stations 509D to send a third NDP552D within a SIFS relative to the second NDP 551D.

In another example implementation, the NDP Poll 510D can initiatemultiple different stations 507D, 508D, 509D to send a multiple NDPs550D, 551D, 552D without an additional NDP Poll where the differentstations 507D, 508D, 509D determine when to send the each of the NDPs550D, 551D, 552D. For example, NDP Poll 510D can be received by multipledifferent stations 507D, 508D, 509D and each station can monitor anetwork channel for a preamble of other dedicated training signals fromother receivers responding to the sounding trigger.

In this example, station 507D can start responding to NDP Poll 510D withNDP 550D, and station 508D can monitor the network channel and listenfor a preamble of NDP 550D. The station 508D can calculate a packetlength of the NDP 550D from listening to the preamble of NDP 550D. Basedon the packet length, station 508D can determine when the channel willbe available next for transmitting the access point 502D and thentransmit an NDPs 551D when the channel is available.

In another example, station 507D and station 508D can contend for themedium prior to sending the NDPs. For example, station 507D and station508D each can attempt to transmit, detect the channel is busy, and waitan amount of time (e.g., a contention window) before attempting totransmit again. In response to a first station 508D detecting thechannel is available, NDP 551D is transmitted while station 507D waitsanother amount of time before attempting to transmit. Then after anotheramount of time, if the second station 507D detects the channel isavailable, NDP 550D is transmitted.

As described above, the NDPs 550D, 551D, 552D response packets arededicated training signals with no user data that can be processed toestimate reverse channel information in the direction from each of thestations 507D, 508D, 509D, to the access point 502D. Then for eachreceived NDPs 550D, 551D, 552D. the access point 502D estimates forwardCSI derived based on the respective NDP to determine the correspondinglink matrix(s) required to adjust the forward channel precoding forsubsequent MIMO transmissions (e.g., user data 566) by the access point502 to the associated target station.

FIG. 5E illustrates an example sequences of solicited sounding with avariable response schedule. The access point 502E can send an NDP Poll510 to multiple different stations 507E, 508E, 509E, or groups ofstations and received multiple NDPs (E.g., 550E, 551E, 552E) within aresponse window (e.g., network allocation vector (NAV) 524).

The access point 502E can establish the response window coordinate withstations responding to the sounding trigger to transmit and blocknon-responding stations from attempting to transmit on the channel. Forexample, the NAV 524 provides a virtual carrier-sensing mechanism tocontrol network access by signaling stations on the network that thechannel is unavailable or busy for a specified contention period. Thestations that are not responding to NDP Poll 510E listen on the wirelessmedium and use a duration field and set their NAV to indicate on howlong it must defer from accessing the medium.

The responding stations 507E, 508E, 509E can respond at different times(e.g., T₁, T₂, T₃, etc.) based on schedule instruction of the NDP Poll510E. The solicited sounding framework supports a variety of schedulingschemes as described herein. For example, the NDP Poll 510E can indicatea sounding position relative to other receiver stations, and eachstation 507E, 508E, 509E can determine one or more response times basedon the sounding position to transmit the one or more dedicated trainingsignals at the calculated response times. In another example, stations507E, 508E, 509E can coordinate sending multiple NDPs 550E, 551E, 552Esequentially by determining a response time based on a packet length ofthe NDP. Each station 507E, 508E, 509E can monitor the channel listenfor a preamble of an NDP from another one of the stations to determinethe packet length of the NDPs. From the determined the packet length ofthe NDPs, a second station 508E can calculate a response time T₂ from areference time such as the last detected NDP preamble.

FIG. 5F illustrates example sequences of solicited sounding with UplinkMU-MIMO communication. An access point with front end RF capableparameters for uplink MU-MIMO communication breaks-up availablebandwidth into separate individual streams (i.e., spatial streams) thatshare the medium equally. With uplink MU-MIMO, an access point canreceive distinct data from two or more stations concurrently over a sameset of OFDM tones. An MU-MIMO access point is characterized by front endparameters (e.g., a number of transmit and receive chains, antenna,etc.) of the transmitter where the capacity to transmit and receive upto n×m communications streams per link of an antenna array.

In an example implementation, an NDP Poll Trigger 510F can solicitmultiple MU-MIMO capable stations 506F, 507F, 508F, 509F tosimultaneously send NDPs (e.g., NDP STA₁, NDP STA₂, . . . , NDP_(N-1),NDP_(N)) on separate spatial streams to a MU-MIMO capable access point502F. The NDP Poll Trigger 510F can indicate or assign a targetedspatial stream for each station 506F, 507F, 508F, 509F to transmit arespective NDPs (e.g., NDP STA₁, NDP STA₂, . . . , NDP_(N-1), NDP_(N))so each of responses is received by the access point 502F at the sametime. The NDP Poll Trigger 510F can also be used by the stations 506F,507F, 508F, 509F as a time reference point to coordinate thesimultaneous transmission of the multiple NDPs (e.g., NDP STA₁, NDPSTA₂, . . . , NDP_(N-1), NDP_(N)) on different spatial streams so thatthe MU-MIMO capable access point 502F can properly process the NDPs(e.g., NDP STA₁, NDP STA₂, . . . , NDP_(N-1), NDP_(N)) to estimateforward channel information.

In an example implementation illustrate by FIG. 5F, a first NDP STA₁ canbe sent by the station 506F on a first spatial stream, a second NDP STA₂can be sent by the station 507F on a second spatial stream, . . . ,NDP_(N-1) can be sent by a station 508F on spatial stream N−1, NDP_(N)can be sent by a station 509F on spatial stream N, and up to the numberof available spatial streams indicated by the access point 502F.

FIG. 5G illustrates an example sequences of solicited sounding withdifferent types of stations. In an example implementation illustrated byFIG. 5G, an NDP Poll 510G can solicit multiple different stations thatgrouped to send dedicated training signals. In one example, differentstations (e.g., 506G-SONG) can be grouped based on their capabilitiesand scheduled to send NDPs at different times.

For example, the NDP Poll 510G can instruct a first group of MU-MIMOcapable stations 506G to SONG to simultaneously send NDPs NDPs (e.g.,NDP STA₁, NDP STA₂, . . . , NDP_(N-1), NDP_(N)) on separate spatialstreams within a first response interval, and further instruct a secondgroup of beamforming capable stations 508G and 509G to sequentially sendNDPs 552G, 553G after the response interval. Example implementations caninclude combinations of different scheduling and training options asdiscussed herein.

FIG. 6 illustrates a flow diagram of an example solicited soundingbeamformee process in accordance with an example implementation.Solicited sounding process 600 for the beamformee can include receivinga sounding trigger at 615 from a wireless transmitter and transmittingat least one dedicated training signal in response to the soundingtrigger 650. In an example, the beamformee receives subsequent packetswith precoding derived from CSI information of the at least onededicated training signal at 655.

In an example implementation, at 625 the beamformee determines aresponse time for transmitting. The beamformee can process a singlesounding trigger to provide multiple dedicated training signals that areused to determine precoding for subsequent packets sent via the forwardchannel from the transmitter. The beamformee can determine the responsetime for transmitting without a sounding schedule by, for example,immediately responding, using contention based transmission, recalling aschedule from memory, monitoring the channel for information from otherstations, etc.

The beamformee can also process the sounding trigger to set a schedulerfor providing additional dedicated training signals and configure thededicated training signals at 620. In an example implementation, thewireless receiver receives the sounding trigger at 615 that indicates asounding schedule at 625 and training options for a format of thededicated training signal. The beamformee stores the sounding scheduleand calculates a response time for each of the one or more dedicatedtraining signals based on the sounding schedule.

In an example implementation, the at least one dedicated training signalfrom the one or more beamformees includes multiple dedicated trainingsignals from an associated beamformee in response to the soundingtrigger. The sounding trigger indicates a sounding schedule foradditional dedicated training signals from the associated beamformee,and the multiple dedicated training signals from the associatedbeamformee are received at timed intervals based on the soundingschedule

The beamformee can also format the dedicated training signals based onthe training options from the sounding trigger at 635. In an example,the beamformee can determine a time to send a dedicated training signalby monitoring network traffic for a preamble of other dedicated trainingsignals from other receivers responding to the sounding trigger. Thenthe beamformee can derive a packet length of the dedicated trainingsignal based on the other dedicated training signals and determine aresponse time based on the packet length.

In another example, where the sounding trigger can indicate a soundingposition relative to other receivers, the beamformee calculates one ormore response times based on the sounding position and transmits the oneor more dedicated training signals at the calculated response times.

FIGS. 7A-B illustrate an example of solicited sounding with timingfeedback in accordance with example implementations. In other exampleimplementations, the beamformee can adapt the solicited soundingframework for streamlining or supporting other networking applications(e.g., motion tracking, building automation, etc.) in addition tosounding. In an example, the beamformee can determine timing feedbackbased on measured time of arrive of the incoming packet and measuredtime of departure of the outgoing packet. Then the beamformee cantransmit a timestamp or other timing information with at least one ofthe dedicated training signals. Including additional timing feedbackwith the dedicated training signal can efficiently synchronize timingbetween stations, ranging functions, etc. with minimal increase totransmission overhead between the beamformee and beamformer.

FIG. 7A illustrates an example sequences of solicited sounding withtiming feedback. In other example implementations, the stations 707,708, 709 can adapt the solicited sounding framework for streamlining orsupporting other networking applications (e.g., motion tracking,building automation, etc.) in addition to sounding. In an example, thestations 707, 708, 709 can determine additional feedback parameters 781,782, 783 that is transmitted to the access point 702E with the NDPs 751,752, 753. For example, stations 751, 752, 753 can determine timingfeedback parameters 781, 782, 783 that are transmitted with the NDPs751, 752, 753 that can be used by the access point 702 for other networkapplications or coordination such as efficiently synchronize timingbetween stations, ranging functions, etc.

The NDPs 751, 752, 753 do not include a payload or user data forsolicited sounding purposes. However, additional feedback timingfeedback parameters 781, 782, 783 can optionally be transmitted withNDPs 751, 752, 753 to streamline or support other networkingapplications (e.g., motion tracking, building automation, etc.) inaddition to sounding. By transmitting additional feedback parameters781, 782, 783 with NDPs 751, 752, 753, the access point 702 can initiatemultiple functions with a single trigger. For example, the access point702 can extract or determine timing information from data (e.g.,additional feedback parameters 781, 782, 783) appended to the NDPs 751,752, 753. The additional feedback parameters 781, 782, 783 are notrequired for and not used by the beamformer to complete the solicitedsounding process. However, by operatively coupling the additionalfeedback parameters 781, 782, 783 appended to the NDPs 751, 752, 753,the number of overhead transmissions between a beamformer and beamformeecan be further reduced.

FIG. 7B illustrates an example time sequences of solicited sounding withtiming feedback. In an example implementation, the station 708determining timing feedback 780 based on measured time of arrival of anincoming packet T₁ and measured time of departure T₂ of an outgoingpacket. In an example, the timing feedback 780 can be the difference inthe times, one or more timestamps or other calculations. The station 708can optionally include the timing feedback 780 as additional information781 during a transmission of an NDP 751 when responding to a NDP Poll710. By transmitting the timing feedback 780 as additional information781 during a transmission of a NDP 751, the solicited sounding frameworkcan be leveraged to eliminate or avoid a separate additionaltransmissions of timing feedback 780 to efficiently provide additionalfunctionality. The beamformee can enable the access point 702 to processother applications 760 in addition to the solicited sounding from thesingle transmission from the station 708 thus increasing availability ofthe channel.

FIGS. 8A-C illustrate an example of sounding solicited by anotherbeamformer in accordance with an example implementation. In an exampleimplementation, solicited sounding by a first beamformer (e.g., accesspoint 802) can enable one or more other beamformers (e.g., station 808)to estimate a forward channel 830 to the same station 809 withoutsending any sounding trigger.

FIG. 8A illustrates an example sequences of solicited sounding inaccordance with an example implementation. In an example where theaccess point 802 is the beamformer sounding beamformee station 809, theaccess point to station (AP-STA) sounding channel can be describedhaving both a AP-STA forward channel 820 from the beamformer accesspoint 802 to the beamformee station 809 and an STA-AP reverse channel821 from the beamformee station 809 to the beamformer access point 802.As discussed above, the beamformer access point 802 can send a singlesounding trigger via the AP-STA forward channel 820 that is received bythe beamformee station 809. The beamformee station 809 can send multiplededicated training signals via the STA-AP reverse channel 821 inresponse to the single sounding trigger from the AP-STA forward channel820 with minimal processing required.

In an example implementation, multiple beamformers can sound one or morebeamformees based on a single solicited sounding trigger. Solicitedsounding by a first beamformer (e.g., access point 802) can enable oneor more other beamformers (e.g., station 808) to estimate a STA-STAforward channel 830 to the same station 809 without sending any soundingtrigger. For example, the first beamformer access point 802 can send asounding trigger via the AP-STA forward channel 820, the beamformeestation 809 can respond with an NDP to the first beamformer access point802 via the STA-AP reverse channel 821 that is overheard by the secondbeamformee station 808 via a STA-STA reverse channel 831.

In an example where the station 808 is a beamformer communicating withbeamformee station 809, the sounding channel can be described havingboth a STA-STA forward channel 830 from the beamformer station 808 tothe beamformee station 809 and a STA-STA reverse channel 831 from thebeamformee station 809 to the beamformer station 808. For example as ina mesh network, the second station 808 can be a beamformee of thebeamformer access point 802 and the second station 808 can be abeamformer of the beamformee station 809 among other combinations.

It should be noted that beamformers and beamformees as well as thechannels are not limited to any number or combination of access pointsand stations. The examples described herein are exemplary and apply toany combinations communication devices with means for beamformersoperations and/or means for beamformees operations.

In some implementation, the second station 808 can also receive thesounding trigger from the first beamformer (e.g., access point 802) viaa second AP forward channel 822. In other implementation, the secondstation 808 can receive the dedicated training signal from the firststation 809 independent of receiving the sounding trigger from theaccess point 802. The second station 808 can monitor a medium (e.g., viaSTA-STA reverse channel 831) for dedicated training signals from abeamformee station 809 to estimate a STA-STA forward channel 830 withoutsending a sounding trigger.

The beamformer station 808 can perform sounding for the STA-STA forwardchannel 830 based on overhearing the dedicated training signal viaSTA-STA reverse channel 831 that was sent by beamformee station 809 toaccess point 802 via AP reverse channel 821.

FIG. 8B illustrates an example sequence of multiple beamformers soundingbeamformees based on a single solicited sounding trigger in accordancewith an example implementation. At 810, access point 802 sends asounding trigger, via the AP-STA forward channel 820, to the firststation 809. At 811, the second station 808 may or may not also receivethe same sounding trigger via another AP-STA forward channel 822.

At 836, the second station monitors a frequency of the STA-STA reversechannel 831 for dedicated training signals. Monitoring the frequency ofSTA-STA reverse channel 831 can detect transmission broadcast or sent onother sounding channels in the network (e.g., the AP-STA forward channel820, the STA-AP reverse channel 821, the STA-STA reverse channel 831,another AP-STA forward channel 822, etc.). At 850, the first station 809sends, via the AP reverse channel 821 one or more dedicated trainingsignals to the access point 802 based on the sounding trigger. At 870,the second station 808 overhears, via the STA-STA reverse channel 831,the one or more dedicated training signals sent by the first station809. At 875, the second station 808 processes the overheard dedicatedtraining signals to estimate a forward CSI for STA-STA forward channel830. At 880, the second station 808 can transmit subsequent packets, viaSTA-STA forward channel 830, to associated beamformee first station 809based on the estimated forward CSI for the STA-STA forward channel 830.

At 860, the access point 802 processes the received dedicated trainingsignals to estimate the forward CSI for the AP-STA forward channel 820.At 866, the access point 802 can transmit subsequent packets, via AP-STAforward channel 820, to associated beamformee first station 809 based onthe estimated forward CSI for the AP-STA forward channel 820. Thus,multiple beamformers can sound one or more beamformees based on a singlesolicited sounding trigger.

FIG. 8C illustrates a flow diagram of an example sequences of asecondary beamformer sounding a beamformee based on a single solicitedsounding trigger from a primary beamformee. The secondary beamformerprocess 840 starts at step 841 where a secondary beamformer (e.g., anon-soliciting beamformer, a piggybacking beamformer, etc.) is tomonitor a communication medium as discussed in reference to FIGS. 8A-B.

At 842, the secondary beamformer process detects at least one dedicatedtraining signal from one or more beamformees in response to a soundingtrigger that was sent by another beamformer (e.g., a primary beamformeror solicitor beamformer). The secondary beamformer does not transmit asounding trigger.

At 843, for each overhead dedicated training signal, the secondarybeamformer process performs steps 844 and 845 to estimate a forwardchannel state information. At step 844, the secondary beamformer processcalculates a CSI for a reverse channel by measuring the receiveddedicated training signal. At 845, the secondary beamformer processderives a CSI for the forward channel, from the CSI of the reversechannel in view of characterization of front end parameters of thetransmitter.

In an example implementation, the secondary beamformer process can usethe estimated forward CSI at 846 to transmit subsequent packets usingprecoded packets with precoding derived from the estimated CSI. Thesecondary beamformer process repeats, at least steps 844 and 845 foreach overhead dedicated training signal associated with a beamformeethat the secondary beamformer intends to communicate with. Accordingly,the solicited sounding framework requires less beamformer processing andless bandwidth than traditional sounding approaches.

FIG. 9 illustrates a diagram of an example networking device or systemthat may be used in connection with various example implementationsdescribed herein. For example the system 915 may be used as or inconjunction with one or more of the mechanisms or processes describedabove, and may represent components of processors, user system(s),and/or other devices described herein. The system 915 can be anetworking device, a router, a server, a laptop, mobile device, or anyconventional computer, or any other processor-enabled device that iscapable of wired or wireless data communication. Other computer systemsand/or architectures may be also used, as will be clear to those skilledin the art.

The system 915 preferably includes one or more processors, such asprocessor 925. Additional processors may be provided, such as anauxiliary processor to manage input/output, an auxiliary processor toperform floating point mathematical operations, a special-purposemicroprocessor having an architecture suitable for fast execution ofsignal processing algorithms (e.g., digital signal processor), a slaveprocessor subordinate to the main processing system (e.g., back-endprocessor), an additional microprocessor or controller for dual ormultiple processor systems, or a coprocessor. Such auxiliary processorsmay be discrete processors or may be integrated with the processor 925.

The processor 925 is preferably connected to a communication bus 920.The communication bus 920 may include a data channel for facilitatinginformation transfer between storage and other peripheral components ofthe system 920. The communication bus 920 further may provide a set ofsignals used for communication with the processor 925, including a databus, address bus, and control bus (not shown). The communication bus 920may comprise any standard or non-standard bus architecture such as, forexample, bus architectures compliant with industry standard architecture(ISA), extended industry standard architecture (EISA), Micro ChannelArchitecture (MCA), peripheral component interconnect (PCI) local bus,or standards promulgated by the Institute of Electrical and ElectronicsEngineers (IEEE) including IEEE 802.11, IEEE 1188 general-purposeinterface bus (GPIB), IEEE 696/S-30, and the like.

Processor(s) 925 can execute under any operating system (OS) (notshown), in a native or virtual environment. One or more applications canbe deployed that include logic unit, application programming interface(API) unit or the like.

System 915 preferably includes a main memory 930 and may also include asecondary memory 935. The main memory 930 provides storage ofinstructions and data for programs executing on the processor 925, suchas one or more of the functions and/or modules discussed above. Itshould be understood that programs stored in the memory and executed byprocessor 925 may be written and/or compiled according to any suitablelanguage, including without limitation C/C++, Java, JavaScript, Pearl,Visual Basic, .NET, and the like. The main memory 930 is typicallysemiconductor-based memory such as dynamic random access memory (DRAM)and/or static random access memory (SRAM). Other semiconductor-basedmemory types include, for example, synchronous dynamic random accessmemory (SDRAM), Rambus dynamic random access memory (RDRAM),ferroelectric random access memory (FRAM), and the like, including readonly memory (ROM).

The secondary memory 935 may optionally include an internal memory 940and/or a removable medium 945, for example a digital versatile disc(DVD) drive, other optical drive, a flash memory drive, etc. Theremovable medium 945 is read from and/or written to in a well-knownmanner. Removable storage medium 945 may be, for example, a floppy disk,magnetic tape, CD, DVD, SD card, etc. The removable storage medium 945is a non-transitory computer-readable medium having stored thereoncomputer executable code (i.e., software) and/or data.

Other examples of secondary memory 935 may include semiconductor-basedmemory such as programmable read-only memory (PROM), erasableprogrammable read-only memory (EPROM), electrically erasable read-onlymemory (EEPROM), or flash memory (block oriented memory similar toEEPROM). Also included are any other removable storage media 945 andcommunication interface 955, which allow software and data to betransferred from an external medium 960 to the system 915.

System 915 may include a communication interface 955. The communicationinterface 955 allows software and data to be transferred between system915 and external devices (e.g., printers), networks, or informationsources. For example, computer software or executable code may betransferred to system 915 from a network server via communicationinterface 955. Examples of communication interface 955 include abuilt-in network adapter, network interface card (NIC), PersonalComputer Memory Card International Association (PCMCIA) network card,card bus network adapter, wireless network adapter, Universal Serial Bus(USB) network adapter, modem, a network interface card (NIC), a wirelessdata card, a communications port, an infrared interface, an IEEE 1394fire-wire, or any other device capable of interfacing system 915 with anetwork or another computing device.

Communication interface 955 preferably implements industry promulgatedprotocol standards, such as Ethernet IEEE 802 standards, Fiber Channel,digital subscriber line (DSL), asynchronous digital subscriber line(ADSL), frame relay, asynchronous transfer mode (ATM), integrateddigital services network (ISDN), personal communications services (PCS),transmission control protocol/Internet protocol (TCP/IP), serial lineInternet protocol/point to point protocol (SLIP/PPP), and so on, but mayalso implement customized or non-standard interface protocols as well.

Software and data transferred via communication interface 955 aregenerally in the form of electrical communication signals 970. Thesesignals 970 are preferably provided to communication interface 955 via acommunication channel 965. In one example implementation, thecommunication channel 965 may be a wired or wireless network, or anyvariety of other communication links. Communication channel 965 carriessignals 970 and can be implemented using a variety of wired or wirelesscommunication means including wire or cable, fiber optics, conventionalphone line, cellular phone link, wireless data communication link, radiofrequency (“RF”) link, or infrared link, just to name a few.

Computer executable code (i.e., computer programs or software) is storedin the main memory 930 and/or the secondary memory 935. Computerprograms can also be received via communication interface 955 and storedin the main memory 930 and/or the secondary memory 935. Such computerprograms, when executed, enable the system 915 to perform the variousfunctions of the present invention as previously described.

For example, communication interface 955 coupled to processor 925 can beconfigured to operate a wireless transceiver including transmitting asounding trigger to one or more receivers, and receiving at least onededicated training signal from the one or more receivers via a reversechannel in response to the sounding trigger. For each received dedicatedtraining signal, it can estimate forward CSI derived based on thededicated training signal from an associated receiver; and whereinsubsequent packets are precoded with precoding derived from the forwardCSI for transmission to the associated receiver via a forward channel.

According to an example implementation, the processor 925 can beconfigured to transmit additional sounding triggers to target additionalreceivers, where a separate additional dedicated training signal isreceived from each of the additional receivers in response to eachadditional sounding trigger, and where for each separate additionaldedicated training signal received, the processor further estimates CSIfor the additional receiver associated with the separate additionaldedicated training signal; and transmits additional steering packets tothe additional receiver based on the CSI. The sounding trigger is notpreceded by an announcement frame and the receiver does not process thesounding trigger to generate detailed sounding feedback (e.g., acompress beamforming feedback based SVD).

In another example, communication interface 955 coupled to processor 925can be configured to operate a wireless receiver including receiving asounding trigger from a wireless transmitter, transmitting at least onededicated training signal in response to the sounding trigger; andreceiving subsequent packets with precoding derived from CSI informationof the at least one dedicated training signal.

Transmitting at least one dedicated training signal in response to thesounding trigger can include transmitting multiple dedicated trainingsignals without receiving another sounding trigger. In an example, thesounding trigger indicates a sounding schedule and training options fora format of the dedicated training signal, and the processor 925 isconfigured store the sounding schedule, calculate a response time foreach of the one or more dedicated training signals based on the soundingschedule, and format the dedicated training signals based on thetraining options. The sounding schedule instructions can indicatesounding times to transmit a dedicated training signal coordinated witha group of receivers (e.g., sequentially, consecutively, simultaneously,in bursts, etc.). In other example implementations, the processor 925 isconfigured to determine the response time to transmit additionaldedicated training signals without receive additional prompting by thebeamformer. In the example, the wireless transceiver can transmitadditional sounding triggers to target additional beamformees. Forexample, additional sounding triggers initiate a series of a separateadditional dedicated training signal from each of the additionalbeamformees. Further, additional sounding triggers initiate a series ofa separate additional dedicated training signal from each of theadditional beamformees in response to each additional sounding trigger.

In an example, operating the wireless transceiver for estimating theforward CSI includes measuring channel information from the dedicatedtraining signal received via the reverse channel, calculating a CSI forthe reverse channel from the measured channel information, and derivingthe forward CSI for the forward channel from the CSI for the reversechannel in view of characteristics of a radio frequency front end of thetransceiver, wherein the subsequent packets are transmitted to theassociated beamformee via the forward channel.

In some examples, a wireless transceiver apparatus includes multiplesets and/or subsets of antenna, a plurality of components coupled to oneanother to form transmit and receive chains, and a solicitor modulecircuit to transmit a sounding trigger, via a forward channel, tosolicit multiple dedicated training signal from one or more beamformees.For example the dedicated training signals can be processed to improvesubsequent transmissions of data to an associated beamformee (e.g.,estimate a forward channel state information (CSI) for transmission ofsubsequent packets to associated beamformee).

The wireless transceiver with the solicitor module circuit generate thesounding trigger that indicates a control scheme (e.g., training optionsfor a format of at least one of the multiple dedicated training signalsbased on communication parameters of a targeted beamformee). Forexample, communication parameters of a targeted beamformee includecombination of one or more of a targeted beamformee capabilities, atraffic type, a positioning parameter, etc.

In further examples, the wireless transceiver with the solicitor modulecircuit may include a sounding module circuit coupled to the pluralityof components. In other examples, a wireless without a transceiversolicitor module circuit may include a sounding module circuit coupledto the plurality of components. The sounding module circuit can processthe dedicated training signals, for example when each received dedicatedtraining signal, the sounding module circuit is to: measure channelinformation of the dedicated training signal received via a reversechannel, calculate a CSI for the reverse channel from the measuredchannel information, and derive the forward CSI for the forward channelfrom the CSI of the reverse channel in view of characteristics of aradio frequency front end of the transceiver.

In other examples, a wireless transceiver apparatus includes multiplesets and/or subsets of antenna, a plurality of components coupled to oneanother to form transmit and receive chains, and a sounding modulecircuit coupled to the multiple sets and/or subsets of antenna. Thewireless transceiver in this example does not require a solicitor modulecircuit and can use dedicated training signals initially initiated byanother wireless transceiver (e.g., a wireless transceiver with asolicitor module circuit). The sounding module circuit can detect atleast one dedicated training signal from the one or more beamformees,wherein the at least one dedicated training signal is based on asounding trigger from another beamformer.

The wireless transceiver apparatus of claim 15, wherein the soundingtrigger indicates a sounding schedule with a time interval configuredbased on communication parameters of a targeted beamformee comprising atleast one of: a targeted beamformee capabilities, a traffic type, and apositioning parameter.

Transmitting the at least one dedicated training signal can be performedby the communications interface 955 at timed intervals based on thesounding schedule indicated by the sounding trigger. In another example.transmitting at least one dedicated training signal can be based onmonitoring for a preamble of other dedicated training signals from otherreceivers responding to the sounding trigger; deriving a packet lengthof the dedicated training signal based on the other dedicated trainingsignals; and determining a response time based on the packet length.

In another embodiment, any of the described examples can includereceiving at least one dedicated training signal with timinginformation. Such timing information can indicate packet transmit andreceive timestamps. The timing information can be used for applicationsother than sounding processes such as motion tracking, location mapping,etc.

In this description, the term “computer readable medium” is used torefer to any non-transitory computer readable storage media used toprovide computer executable code (e.g., software and computer programs)to the system 915. Examples of these media include main memory 930,secondary memory 935 (including internal memory 940, removable medium945, and external storage medium 945), and any peripheral devicecommunicatively coupled with communication interface 955 (including anetwork information server or other network device). Thesenon-transitory computer readable mediums are means for providingexecutable code, programming instructions, and software to the system915.

In an example implementation that is implemented using software, thesoftware may be stored on a computer readable medium and loaded into thesystem 915 by way of removable medium 945, I/O interface 950, orcommunication interface 955. In such an example implementation, thesoftware is loaded into the system 915 in the form of electricalcommunication signals 970.

In an example implementation, I/O interface 950 provides an interfacebetween one or more components of system 915 and one or more inputand/or output devices. Example input devices include, withoutlimitation, keyboards, touch screens or other touch-sensitive devices,biometric sensing devices, computer mice, trackballs, pen-based pointingdevices, and the like.

The system 915 also includes optional wireless communication componentsthat facilitate wireless communication over a voice and over a datanetwork. The wireless communication components comprise an antennasystem 975, a radio system 980, and a baseband system 985. In the system915, radio frequency (RF) signals are transmitted and received over theair by the antenna system 975 under the management of the radio system980.

In one example implementation, the antenna system 975 may comprise oneor more antennae and one or more multiplexors (not shown) that perform aswitching function to provide the antenna system 975 with transmit andreceive signal paths. In the receive path, received RF signals can becoupled from a multiplexor to a low noise amplifier (not shown) thatamplifies the received RF signal and sends the amplified signal to theradio system 980.

In alternative example implementations, the radio system 980 maycomprise one or more radios that are configured to communicate overvarious frequencies. In one example implementation, the radio system 980may combine a demodulator (not shown) and modulator (not shown) in oneintegrated circuit (IC). The demodulator and modulator can also beseparate components. In the incoming path, the demodulator strips awaythe RF carrier signal leaving a baseband receive audio signal, which issent from the radio system 980 to the baseband system 985.

If the received signal contains audio information, then baseband system985 decodes the signal and converts it to an analog signal. Then thesignal is amplified and sent to a speaker. The baseband system 985 alsoreceives analog audio signals from a microphone. These analog audiosignals are converted to digital signals and encoded by the basebandsystem 985. The baseband system 985 also codes the digital signals fortransmission and generates a baseband transmit audio signal that isrouted to the modulator portion of the radio system 980. The modulatormixes the baseband transmit audio signal with an RF carrier signalgenerating an RF transmit signal that is routed to the antenna systemand may pass through a power amplifier (not shown). The power amplifieramplifies the RF transmit signal and routes it to the antenna system 975where the signal is switched to the antenna port for transmission.

The baseband system 985 is also communicatively coupled with theprocessor 925. The central processing unit 925 has access to datastorage areas 930 and 935. The central processing unit 925 is preferablyconfigured to execute instructions (i.e., computer programs or software)that can be stored in the memory 930 or the secondary memory 935.Computer programs can also be received from the baseband processor 985and stored in the data storage area 930 or in secondary memory 935, orexecuted upon receipt. Such computer programs, when executed, enable thesystem 915 to perform the various functions of the present invention aspreviously described. For example, data storage areas 930 may includevarious software modules (not shown).

Some portions of the detailed description are presented in terms ofalgorithms and symbolic representations of operations within a computer.These algorithmic descriptions and symbolic representations are themeans used by those skilled in the data processing arts to convey theessence of their innovations to others skilled in the art. An algorithmis a series of defined operations leading to a desired end state orresult. In example implementations, the operations carried out requirephysical manipulations of tangible quantities for achieving a tangibleresult.

Unless specifically stated otherwise, as apparent from the discussion,it is appreciated that throughout the description, discussions utilizingterms such as detecting, determining, analyzing, identifying, scanningor the like, can include the actions and processes of a computer systemor other information processing device that manipulates and transformsdata represented as physical (electronic) quantities within the computersystem's registers and memories into other data similarly represented asphysical quantities within the computer system's memories or registersor other information storage, transmission or display devices.

Example implementations may also relate to an apparatus for performingthe operations herein. This apparatus may be specially constructed forthe required purposes, or it may include one or more general-purposecomputers selectively activated or reconfigured by one or more computerprograms.

An example apparatus can include a Wireless Access Point (WAP) or astation and incorporating a very-large-scale integration (VLSI)processor and program code to support. An example transceiver couplesvia an integral modem to one of a cable, fiber or digital subscriberbackbone connection to the Internet to support wireless communications,e.g., IEEE 802.11 compliant communications, on a Wireless Local AreaNetwork (WLAN). The Wi-Fi stage includes a baseband stage, and theanalog front end (AFE) and Radio Frequency (RF) stages. In the basebandportion wireless communications transmitted to or received from eachuser/client/station are processed. The AFE and RF portion handles theupconversion on each of transmit paths of wireless transmissionsinitiated in the baseband. The RF portion also handles thedownconversion of the signals received on the receive paths and passesthem for further processing to the baseband.

The WAP and/or station can support multiple protocols and multilingualwith the ability to communicate with multiple protocols, for exampleInternet of Things protocols including Bluetooth-Low-Energy, Zigbee,Thread, etc. and communicatively coupled to one or more resources foraccess to analytics or machine-learning capabilities. In someimplementations, the WAP and/or station is battery powered and mobile orintegrated a larger mobile device such as an automobile or airplane.

An example apparatus can be multiple-input multiple-output (MIMO)apparatus supporting as many as N×N discrete communication streams overN antennas. In an example the MIMO apparatus signal processing units canbe implemented as N×N. In various examples, the value of N can be 4, 6,8, 12, 16, etc. Extended MIMO operation enable the use of up to 2Nantennae in communication with another similarly equipped wirelesssystem. It should be noted that extended MIMO systems can communicatewith other wireless systems even if the systems do not have the samenumber of antennae, but some of the antennae of one of the stationsmight not be utilized, reducing optimal performance.

In some implementations, beamforming antenna configuration soundingdiscussed herein, may be applied with equal advantage to WAPs orstations with any number of transmit chains, receive chains, or MIMOantenna, including but not limited to: 1×2, 1×n, 2×3, 2×4, 2×n, 3×4,3×n, 4×5, 4×8, 4×n, 8×9, 8×16, 8×n, etc.; without departing from thedisclosure. The components and processes disclosed herein may beimplemented in a combination of software, circuits, hardware, andfirmware, integrated with the WAP's existing transmit and receive pathcomponents, and without departing from the scope of the disclosure.

Example transmit path/chain includes the following discrete and sharedcomponents. A Wi-Fi medium access control (WMAC) component includes:hardware queues for each downlink and uplink communication stream;encryption and decryption circuits for encrypting and decrypting thedownlink and uplink communication streams; medium access circuit formaking the clear channel assessment (CCA), and making exponential randombackoff and re-transmission decisions; and a packet processor circuitfor packet processing of the transmitted and received communicationstreams. The WMAC component has access to a node table which lists eachnode/station on the WLAN, the station's capabilities, the correspondingencryption key, and the priority associated with its communicationtraffic.

Each sounding or data packet for wireless transmission on the transmitpath components to one or more stations is framed in the framer. Nexteach stream is encoded and scrambled in the encoder and scramblerfollowed by demultiplexing in demultiplexer into separate streams. Nextstreams are subject to interleaving and mapping in a corresponding oneof the interleaver mappers. Next all transmissions are spatially mappedwith a spatial mapping matrix (SMM) in the spatial mapper. The spatiallymapped streams from the spatial mapper are input to Inverse DiscreteFourier Transform (IDFT) components for conversion from the frequency tothe time domain and subsequent transmission in the AFT and RF stage.

A IDFT is coupled to a corresponding one of the transmit path/chaincomponents in the AFT RF stage for wireless transmission on anassociated one of MIMO antenna. Specifically each IDFT couples to anassociated one of the digital-to-analog converters (DAC) 550 forconverting the digital transmission to analog, filters, upconverters,coupled to a common voltage controlled oscillator (VCO) for upconvertingthe transmission to the appropriate center frequency of the selectedchannel(s), and power amplifiers for setting the transmit power level ofthe transmission on the MIMO antenna array.

The receive path/chain includes the following discrete and sharedcomponents. Received communications on the WAP's array of MIMO antennaare subject to RF processing including downconversion in the AFE-RFstage. There are six receive paths each including the following discreteand shared components: low noise amplifiers (LNA) for amplifying thereceived signal under control of an analog gain control (AGC) (notshown) for setting the amount by which the received signal is amplified,downconverters coupled to the VCO for downconverting the receivedsignals, filters for bandpass filtering the received signals,analog-to-digital converters (ADC) for digitizing the downconvertedsignals. In an example implementation, an optional sampler 568 at theoutput of the ADCs allows sampling of the received Wi-Fi signals in thetime domain, for subsequent Wi-Fi spatial diagnostics by the processorand non-volatile memory. The digital output from each ADC is passed to acorresponding one of the discrete Fourier transform (DFT) components inthe baseband portion of the Wi-Fi stage for conversion from the time tothe frequency domain.

Receive processing in the baseband stage includes the following sharedand discrete components including: an equalizer to mitigate channelimpairments which is coupled to the output of the DFTs. In an exampleimplementation, the received Wi-Fi signals in the frequency domain fromthe output of the DFTs either with or without equalization are providedto the processor and non-volatile memory. The received Wi-Fi streams atthe output of the equalizer are subject to demapping and deinterleavingin a corresponding number of the demappers and deinterleavers. Next thereceived stream(s) are multiplexed in multiplexer and decoded anddescrambled in the decoder and descrambler component, followed byde-framing in the deframer. The received communication is then passed tothe WMAC component where it is decrypted with the decryption circuit andplaced in the appropriate upstream hardware queue for upload to theInternet.

A non-transitory computer-readable storage medium may involve tangiblemediums such as, but not limited to optical disks, magnetic disks,read-only memories, random access memories, solid state devices anddrives, or any other types of tangible or non-transitory media suitablefor storing electronic information. A computer readable signal mediummay include mediums such as carrier waves. The algorithms and displayspresented herein are not inherently related to any particular computeror other apparatus. Computer programs can involve pure softwareimplementations that involve instructions that perform the operations ofthe desired implementation.

A computing device can be communicatively coupled to input/userinterface and output device/interface. Either one or both of input/userinterface and output device/interface can be a wired or wirelessinterface and can be detachable. Input/user interface may include anydevice, component, sensor, or interface, physical or virtual, that canbe used to provide input (e.g., buttons, touchscreen interface,keyboard, a pointing/cursor control, microphone, camera, braille, motionsensor, optical reader, and/or the like).

The term “communicatively connected” is intended to include any type ofconnection, wired or wireless, in which data may be communicated. Theterm “communicatively connected” is intended to include, but not limitedto, a connection between devices and/or programs within a singlecomputer or between devices and/or separate computers over the network.The term “network” is intended to include, but not limited to,packet-switched networks such as local area network (LAN), wide areanetwork (WAN), TCP/IP, (the Internet), and can use various means oftransmission, such as, but not limited to, Wi-Fi®, Bluetooth®, Zigbee®,Internet Protocol version 6 over Low power Wireless Area Networks(6LowPAN), power line communication (PLC), Ethernet (e.g., 10 Megabyte(Mb), 100 Mb and/or 1 Gigabyte (Gb) Ethernet) or other communicationprotocols.

Further, some example implementations of the present application may beperformed solely in hardware, whereas other functions may be performedsolely in software. Moreover, the various functions described can beperformed in a single unit, or can be spread across a number ofcomponents in any number of ways. When performed by software, themethods may be executed by a processor, such as a general purposecomputer, based on instructions stored on a computer-readable medium. Ifdesired, the instructions can be stored on the medium in a compressedand/or encrypted format.

The example implementations may have various differences and advantagesover related art. Moreover, other implementations of the presentapplication will be apparent to those skilled in the art fromconsideration of the specification and practice of the teachings of thepresent application. Various aspects and/or components of the describedexample implementations may be used singly or in any combination. It isintended that the specification and example implementations beconsidered as examples only, with the true scope and spirit of thepresent application being indicated by the following claims.

What is claimed is:
 1. A method performed by a wireless transceiverapparatus for a wireless local area network (WLAN) supporting wirelesscommunications, the wireless transceiver apparatus including componentscoupled to one another to form transmit and receive chains, the methodcomprising: detecting at least one dedicated training signal from one ormore beamformees, wherein the at least one dedicated training signal isbased on a sounding trigger from another beamformer different from thewireless transceiver apparatus, the at least one dedicated trainingsignal transmitted without a payload and including information used tosupport a networking application other than sounding such that the atleast one dedicated training signal is usable for beamforming and thenetworking application other than sounding, the sounding triggerincluding training options for at least one of the one or morebeamformees to format at least one of the at least one dedicatedtraining signals including repeated symbols, partial bandwidth, and anumber of bits.
 2. The method of claim 1, further comprising monitoringa communication medium over which the at least one dedicated trainingsignal is detected.
 3. The method of claim 1, further comprisingcalculating reverse channel information for a reverse channel bymeasuring the at least one dedicated training signal.
 4. The method ofclaim 1, further comprising deriving forward channel information for aforward channel.
 5. The method of claim 4, wherein the forward channelinformation is based on reverse channel information in view ofcharacterization of one or more front end parameters of the wirelesstransceiver apparatus, the reverse channel information determined basedon measuring the at least one dedicated training signal.
 6. The methodof claim 4, further comprising transmitting subsequent packets to theone or more beamformees using packets precoded with precoding based onthe derived forward channel information.
 7. The method of claim 1,wherein the wireless transceiver apparatus is configured not to transmitsounding triggers.
 8. One or more non-transitory computer readablemedium containing instructions that, when executed by one or moreprocessors of a wireless transceiver apparatus of a wireless local areanetwork (WLAN) supporting wireless communications, are configured toperform operations, the wireless transceiver apparatus includingcomponents coupled to one another to form transmit and receive chains,the operations comprising: detecting at least one dedicated trainingsignal from one or more beamformees, wherein the at least one dedicatedtraining signal is based on a sounding trigger from another beamformerdifferent from the wireless transceiver apparatus, the dedicatedtraining signal transmitted without a payload and including timinginformation, the sounding trigger including training options for atleast one of the one or more beamformees to format at least one of theat least one dedicated training signals including repeated symbols,partial bandwidth, and a number of bits.
 9. The non-transitory computerreadable medium of claim 8, wherein the operations further comprisemonitoring a communication medium over which the at least one dedicatedtraining signal is detected.
 10. The non-transitory computer readablemedium of claim 8, wherein the operations further comprise calculatingreverse channel information for a reverse channel by measuring the atleast one dedicated training signal.
 11. The non-transitory computerreadable medium of claim 8, wherein the operations further comprisederiving forward channel information for a forward channel.
 12. Thenon-transitory computer readable medium of claim 11, wherein the forwardchannel information is based on reverse channel information in view ofcharacterization of one or more front end parameters of the wirelesstransceiver apparatus, the reverse channel information determined basedon measuring the at least one dedicated training signal.
 13. Thenon-transitory computer readable medium of claim 11, wherein theoperations further comprise transmitting subsequent packets to the oneor more beamformees using packets precoded with precoding based on thederived forward channel information.
 14. The non-transitory computerreadable medium of claim 8, wherein the wireless transceiver apparatusis configured not to transmit sounding triggers.
 15. A method foroperating a wireless transceiver, comprising: transmitting a singlesounding trigger to one or more beamformees via a forward channel, thesingle sounding trigger including instructions for an associatedbeamformee of the one or more beamformees to transmit multiplesuccessive dedicated training signals and training options for theassociated beamformee to format the dedicated training signals includingrepeated symbols, partial bandwidth, and a number of bits; and receivingat least one dedicated training signal from the one or more beamformeesvia a reverse channel in response to the single sounding trigger,including receiving the multiple successive dedicated training signalsfrom the associated beamformee responsive to the single soundingtrigger, the at least one dedicated training signal includinginformation used to support a networking application other thansounding.
 16. The method for operating the wireless transceiver of claim15, wherein for each of the at least one received dedicated trainingsignals: estimating forward channel state information (CSI) derivedbased on the dedicated training signal from the associated beamformee;and wherein subsequent packets are precoded with precoding derived fromthe forward CSI for transmission to the associated beamformee via theforward channel.
 17. The method for operating the wireless transceiverof claim 16, wherein estimating the forward CSI comprises: measuringchannel information from the dedicated training signal received via thereverse channel; calculating a CSI for the reverse channel from themeasured channel information; and deriving the forward CSI for theforward channel from the CSI for the reverse channel in view ofcharacteristics of a radio frequency front end of the transceiver,wherein the subsequent packets are transmitted to the associatedbeamformee via the forward channel.
 18. The method for operating thewireless transceiver of claim 15, wherein receiving at least onededicated training signal from the one or more beamformees comprises:receiving multiple dedicated training signals from different beamformeesin response to the single sounding trigger.
 19. The method for operatingthe wireless transceiver of claim 18, wherein the multiple dedicatedtraining signals are received sequentially from the differentbeamformees, and wherein each of the different beamformees determine aresponse time based on a packet length of the dedicated training signalin view of the single sounding trigger.
 20. The method for operating thewireless transceiver of claim 18, wherein the single sounding triggerindicates a separate spatial stream for each of the differentbeamformees to send the dedicated training signal; and wherein themultiple dedicated training signals are received simultaneously from thedifferent beamformees on separate spatial streams.
 21. The method foroperating the wireless transceiver of claim 15, wherein the singlesounding trigger indicates a sounding schedule comprising at least oneof: a sounding interval, a sounding position, and a schedule expiration.22. The method for operating the wireless transceiver of claim 21,wherein the sounding schedule indicates sounding times for a group ofbeamformees to send dedicated training signals via the reverse channel.23. The method for operating the wireless transceiver of claim 15,wherein the single sounding trigger indicates a sounding schedule foradditional dedicated training signals from the associated beamformee,and wherein the multiple successive dedicated training signals from theassociated beamformee are received at timed intervals based on thesounding schedule.
 24. The method for operating the wireless transceiverof claim 15, wherein the single sounding trigger indicates stationinformation to enable different beamformees to send multiple dedicatedtraining signals, wherein the station information comprising at leastone of: a station list, a station identifier, and MAC address.
 25. Themethod for operating the wireless transceiver of claim 15, furthercomprising: transmitting additional sounding triggers to targetadditional beamformees, wherein a separate additional dedicated trainingsignal is received from each of the additional beamformees in responseto each additional sounding trigger.
 26. The method for operating thewireless transceiver of claim 15, wherein the single sounding trigger isnot preceded by an announcement frame, and the dedicated training signalis a null data packet.
 27. A wireless transceiver apparatus for awireless local area network (WLAN) supporting wireless communications,and the wireless transceiver apparatus comprising: a plurality ofcomponents coupled to one another to form transmit and receive chains;and a solicitor module circuit configured to transmit a single soundingtrigger, via a forward channel, to solicit multiple dedicated trainingsignal from one or more beamformees including multiple successivededicated training signals from an associated beamformee responsive tothe single sounding trigger and including timing information, whereinthe dedicated training signals are processed to estimate a forwardchannel state information (CSI) for transmission of subsequent packetsto respective beamformees, the single sounding trigger includingtraining options for the associated beamformee to format the dedicatedtraining signal including repeated symbols, partial bandwidth, and anumber of bits.
 28. The wireless transceiver apparatus of claim 27,further comprising a sounding module circuit coupled to the plurality ofcomponents, wherein for each received dedicated training signal, thesounding module circuit is further configured to: measure channelinformation of the dedicated training signal received via a reversechannel; calculate a CSI for the reverse channel from the measuredchannel information; and derive the forward CSI for the forward channelfrom the CSI of the reverse channel in view of characteristics of aradio frequency front end of the transceiver.
 29. The wirelesstransceiver apparatus of claim 27, wherein the single sounding triggerindicates training options for a format of at least one of the multiplededicated training signals based on communication parameters of atargeted beamformee comprising at least one of: a targeted beamformeecapabilities, a traffic type, and a positioning parameter.
 30. Thewireless transceiver apparatus of claim 27, wherein the single soundingtrigger indicates a sounding schedule with a time interval configuredbased on communication parameters of a targeted beamformee comprising atleast one of: a targeted beamformee capabilities, a traffic type, and apositioning parameter.
 31. A method for operating a wirelesstransceiver: transmitting a single sounding trigger to one or morebeamformees via a forward channel the single sounding trigger includinginstructions for an associated beamformee of the one or more beamformeesto transmit multiple successive dedicated training signals and trainingoptions for the associated beamformee to format the dedicated trainingsignals including repeated symbols, partial bandwidth, and a number ofbits; and receiving at least one dedicated training signal with timinginformation from the one or more beamformees via a reverse channel inresponse to the single sounding trigger, including receiving themultiple successive dedicated training signals from the associatedbeamformee responsive to the single sounding trigger; wherein the timinginformation indicates packet transmit and receive timestamps.